This section provides background information related to the present disclosure and is not necessarily prior art.
In an attempt to reduce the quantity of NOX and particulate matter emitted to the atmosphere during internal combustion engine operation, a number of exhaust aftertreatment devices have been developed. A need for exhaust aftertreatment systems particularly arises when diesel combustion processes are implemented. Typical aftertreatment systems for diesel engine exhaust may include one or more of a diesel particulate filter (DPF), a selective catalytic reduction (SCR) system, a hydrocarbon (HC) injector, and a diesel oxidation catalyst (DOC).
During engine operation, the DPF traps soot emitted by the engine and reduces the emission of particulate matter (PM). Over time, the DPF becomes loaded and begins to clog. Periodic regeneration or oxidation of the trapped soot in the DPF is required for proper operation. To regenerate the DPF, relatively high exhaust temperatures in combination with an ample amount of oxygen in the exhaust stream are needed to oxidize the soot trapped in the filter.
The DOC is typically used to generate heat to regenerate the soot loaded DPF. When hydrocarbons (HC) are sprayed over the DOC at or above a specific light-off temperature, the HC will oxidize. This reaction is highly exothermic and the exhaust gases are heated during light-off. The heated exhaust gases are used to regenerate the DPF.
Under many engine operating conditions, however, the exhaust gas is not hot enough to achieve a DOC light-off temperature of approximately 300° C. As such, DPF regeneration does not passively occur. Furthermore, NOX adsorbers and selective catalytic reduction systems typically require a minimum exhaust temperature to properly operate. Therefore, a burner may be provided to heat the exhaust stream upstream of the various aftertreatment devices to a suitable temperature to facilitate DOC light-off, regeneration and efficient operation of the aftertreatment devices. While burners have been associated with exhaust treatment systems in the past, it may be beneficial to provide an improved burner and mixer system to provide improved ignition at very low temperatures, improved heat transfer between the exhaust gas and the burner, improved fuel efficiency and/or energy usage, and robust longevity.